linux-kernel - Re: [PATCH] mm/mincore: allow for making sys

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Message-ID: <CA+t-nXTfdo07EBvVo+mu8SRhrVyB=mEPLDQikHfpJue1jALJtQ@mail.gmail.com>
Date:   Tue, 15 Jan 2019 23:52:25 -0800
From:   Josh Snyder <joshs@...flix.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Chinner <david@...morbit.com>,
        Jiri Kosina <jikos@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>, Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

On Tue, Jan 15, 2019 at 10:34 PM Dominique Martinet <asmadeus@...ewreck.org>
wrote:
>
> There is a difference with your previous patch though, that used to list no
> page in core when it didn't know; this patch lists pages as in core when it
> refuses to tell. I don't think that's very important, though.

Is there a reason not to return -EPERM in this case?

>
> If anything, the 0400 user-owner file might be a problem in some edge
> case (e.g. if you're preloading git directories, many objects are 0444);
> should we *also* check ownership?...

Yes, this seems valuable. Some databases with immutable files (e.g. git, as
you've mentioned) conceivably operate this way.

Josh